Impairment of cochlear blood flow (CBF) likely induces many types of sensorineural hearing loss. In particular, disruption of the internal auditory artery (IAA) during operations to remove vestibular schwannomas (acoustic neuromas) probably accounts for many cases of postoperative deafness. Although CBF has been successfully measured using laser-Doppler (LD) flowmetry in animal experiments, these models have not permitted a direct application to humans, primarily due to differences in the translucence of the otic capsule between species. Experiments in this laboratory have shown that changes in CBF can be reliably measured from the round window of rabbits using LD. Furthermore, these studies have demonstrated excellent correlation between LD measurements of changes in CBF and both physical obstruction of the IAA and physiologic measures of cochlear function using otoacoustic emissions. In order to apply LD techniques to measure changes in CBF in humans, a group composed of optical scientists, electrical engineers and otologic surgeons has designed an otic probe, which will fit into the round window and enable measurement of changes in CBF and cochlear potentials. Prototype versions of the probe will be tested in the rabbit preparation for safety and reliability in the measurement of CBF during experimental manipulations of the IAA. PROPOSED COMMERCIAL APPLICATIONS: The research will develop a transtympanic otic probe that will measure cochlear blood flow utilizing LaserDoppler velocimetry and auditory evoked potentials using electrocochleography. The results will lead to the manufacture of an effective neurocochlear monitoring device which will be used in surgical procedures involving brainstem structures and clinical diagnosis of hearing loss.